Understanding influences of angler proximity on fisheries resources, in the distances anglers are willing to travel for angling opportunities and their success rates after they arrive, could influence fisheries resiliency and management applications. The Wisconsin Department of Natural Resources, Northern Highland Fishery Research Area (NHFRA), Vilas County, Wisconsin maintains a compulsory creel census that collects angler ZIP code information and species-specific angler catch rates from all visiting anglers. We used NHFRA angler ZIP code data from 2014 to 2019 on Escanaba, Nebish, and Pallette lakes to construct anglershed maps (i.e., highest density areas from which anglers traveled to fish the lakes) for muskellunge (Esox masquinongy), smallmouth bass (Micropterus dolomieu), walleye (Sander vitreus), and yellow perch (Perca flavescens) to better understand angler travel patterns. We then tested for differences in species-specific catch rates among local (from counties surrounding or adjacent to the lakes, <100-km away), non-local (from counties in southern Wisconsin, >350-km away), and non-Wisconsin resident anglers. We hypothesized that local anglers would have higher overall species-specific catch rates due to proximity to the lakes and local knowledge than non-local or non-resident anglers. Anglersheds showed high use of the lakes by non-local anglers associated with major population centers in southern Wisconsin (Dane and Milwaukee counties) and adjacent states (Illinois and Minnesota). Species-specific catch rates did not differ appreciably among local, non-local, and non-resident anglers. Our results suggest that local knowledge may not be a good indicator of fishing trip success or elevated catch rates. Technology and angler information sources may level the playing field for anglers resulting in the homogenization of catch rates. Therefore, distance from a fishery may not aid in strengthening fisheries resilience.

Due to time and resource limitations, the growth of many fish species is evaluated with age and length data in a length-stratified subsample of a sample from a population. Some fisheries professionals draw inferences about growth using age and length data from only those fish that were actually aged (aged-only method). Alternatively, growth may be evaluated by employing a method of incorporating the length-stratified aged subsample with information from the entire sample of fish collected, such as the weighted-mean and assigned-age methods, which are commonly used in inland fisheries management. More recently, two prominent alternatives to those methods have emerged: the reweighting and empirical proportion methods. In this study, we used observed data from three freshwater fish species with different life history traits (short- to long-lived) to inform a simulation model comparing estimated von Bertalanffy growth model parameters and predicted mean lengths at age calculated using the five aforementioned methods across a range of sample sizes per length-group and a range of CVs. As expected, our results demonstrated that the aged-only method is unreliable and biased when estimating von Bertalanffy parameters and mean lengths at age. The weighted-mean method performed better than the aged-only method but was not among the top-performing methods. The assigned-age, reweighting, and empirical proportion methods all performed well and produced similar estimates, although the empirical proportion method generally resulted in slightly more precise and less biased estimates. We recommend that fisheries professionals discontinue their use of the aged-only and weighted-mean methods and instead use the assigned-age, reweighting, or empirical proportion method.

Arctic charr (Salvelinus alpinus (Linnaeus, 1758)) are phenotypically plastic with multiple dietary–morphological relationships observed throughout their circumpolar range. Feeding strategies often differ between Arctic charr life histories and can impact size-at-age and morphological attributes. We examined growth, condition, and body morphology for two High Arctic populations of Arctic charr with anadromous and landlocked life histories. Anadromous Arctic charr had higher growth rates, achieving mean lengths two times those of landlocked Arctic charr by age 10 and had higher overall condition, particularly in the fall. Ontogenetic shifts in diet were suspected in both populations, with an abrupt shift to marine feeding in the anadromous population and a gradual shift to piscivory in the landlocked population. Morphological differences between life histories manifested most predominantly in larger eye diameter, longer pectoral and pelvic fins, and longer upper jaws of landlocked Arctic charr, suggestive of piscivorous feeding specialization of landlocked fish >350 mm. Our findings emphasize the benefits that marine feeding can have for growth and condition of freshwater fishes in Arctic environments and also convey the necessity of adaptive feeding strategies to optimize growth and condition in fishes inhabiting low-production lacustrine habitats.

The Laurentian Great Lakes have experienced recent ecosystem changes that could lead to reductions in adaptive capacity and ultimately a loss of biodiversity and production throughout the food web. Observed changes in Great Lakes benthic communities include declines of native species and widespread success of invasive species like dreissenid mussels in all but Lake Superior. Understanding the ecology of native benthic deepwater preyfish and the reasons for their declines is important for predicting future losses in adaptive capacity and diversity, as well as managing the Great Lakes ecosystem to avoid such losses. Native sculpin species (Cottus bairdii,C. cognatus,C. ricei,Myoxocephalus thompsonii) historically were among the most abundant of the Great Lakes native deepwater benthic preyfish community and are an important link between offshore benthic and pelagic food webs. With one exception, these species have declined in abundance throughout the Great Lakes in recent years, but relatively little is known about their biology and ecology. This review synthesizes the available knowledge for the Great Lakes sculpin species and provides suggestions for future research efforts, which include understanding reproductive ecology and spawning behavior, connectivity and dispersal of populations, early life history, and influences of interactions with native and non-native species.

Growth is an important metric in fisheries and aquaculture. Growth of small fish over relatively short periods of time is commonly modelled with an exponential function using instantaneous growth rate (g). Instantaneous growth rates are logarithmic and inherently difficult to interpret, but specific growth rates (SGR) express growth as the intuitively understandable per cent change in size per unit of time. A simple metric of SGR (G) is easily computed by exponentiating g, subtracting 1 and multiplying by 100. However, several prominent fisheries publications suggest that SGR should be calculated by simply multiplying g by 100 (we call this G*). A search of the fisheries literature found that the number of papers that used SGR for fish increased significantly from 1830 papers in 2009 to 3170 papers in 2018. An extensive review of 300 papers from this search found that 92.6% were related to aquaculture and only 3.3% of all papers correctly used G to calculate SGR. We algebraically show that G* is fundamentally different than G and cannot be interpreted as a per cent change in weight per unit of time. Furthermore we demonstrate, with three examples from the literature, that using G* as if it were the same as G leads to biologically meaningful underestimates of true growth rates and estimated weights. Given these results and the simplicity with which G can be computed from g, we recommend that fisheries scientists abandon the pervasive practice of incorrectly measuring SGR as 100 times the instantaneous growth rate.

Recreational fisheries are valued at $190B globally and constitute the predominant way in which people use wild fish stocks in developed countries, with inland systems contributing the main fraction of recreational fisheries. Although inland recreational fisheries are thought to be highly resilient and self-regulating, the rapid pace of environmental change is increasing the vulnerability of these fisheries to overharvest and collapse. Here we directly evaluate angler harvest relative to the biomass production of individual stocks for a major inland recreational fishery. Using an extensive 28-y dataset of the walleye (Sander vitreus) fisheries in northern Wisconsin, United States, we compare empirical biomass harvest (Y) and calculated production (P) and biomass (B) for 390 lake year combinations. Production overharvest occurs when harvest exceeds production in that year. Biomass and biomass turnover (P/B) declined by ∼30 and ∼20%, respectively, over time, while biomass harvest did not change, causing overharvest to increase. Our analysis revealed that ∼40% of populations were production-overharvested, a rate >10× higher than estimates based on population thresholds often used by fisheries managers. Our study highlights the need to adapt harvest to changes in production due to environmental change.

Little is known about populations of Stonecat Noturus flavus, especially in the northeastern United States, where they are at the edge of their range. In Lake Champlain tributaries, Stonecats are listed as endangered in Vermont but not in New York. Here we describe the growth of Stonecats in two tributaries to Lake Champlain, one in Vermont (LaPlatte River), which was our primary interest, and one in New York (Great Chazy River), with von Bertalanffy growth models fit to lengths at the times of marking and recapture and to observed length and age data. We also compared growth of Stonecats in these waters to results from other locations near the middle of their distribution. Stonecats in the Great Chazy River were larger at ages 1-3, but similar in size for ages 4 and 5, than Stonecats from the LaPlatte River. Stonecats in Lake Champlain tributaries were generally larger at age than those from the middle of their range, except for those from Lake Erie. From our mean length-at-age results and previous literature estimates of length at maturity for Stonecats, it appears that Stonecats in Lake Champlain reach maturity by age 3, though future research that directly estimates age at maturity would be more informative. These results will help managers assess the effect of various environmental and human stressors that Stonecats have experienced in the Lake Champlain basin in recent years. Furthermore, our results expand the literature, which lacks information about growth of this species. Finally, our mark-recapture approach to estimating growth of Stonecats can be applied to other species, especially where data are limited because of their status, and in other systems.

Age estimates of Lake Superior Kiyis Coregonus kiyi from scales and otoliths were compared and 12 years (2003-2014) of length frequency data were examined to assess year-class strength and validate age estimates. Ages estimated from otoliths were precise and were consistently older than ages estimated from scales. Maximum otolith-derived ages were 20 years for females and 12 years for males. Age estimates showed high numbers of fish of ages 5, 6, and 11 in 2014, corresponding to the 2009, 2008, and 2003 year-classes, respectively. Strong 2003 and 2009 year-classes, along with the 2005 year-class, were also evident based on distinct modes of age-1 fish (< 110 mm) in the length frequency distributions from 2004, 2010, and 2006, respectively. Modes from these year-classes were present as progressively larger fish in subsequent years. Few to no age-1 fish (< 110 mm) were present in all other years. Ages estimated from otoliths were generally within 1 year of the ages corresponding to strong year-classes, at least for age-5 and older fish, suggesting that Kiyi age may be reliably estimated to within 1 year by careful examination of thin-sectioned otoliths.

Estimating the time required (i.e., age) for fish in a population to reach a specific length (e.g., legal harvest length) is useful for understanding population dynamics and simulating the potential effects of length-based harvest regulations. The age at which a population reaches a specific mean length is typically estimated by fitting a von Bertalanffy growth function to length-at-age data and then rearranging the best-fit equation to solve for age at the specified length. This process precludes the use of standard frequentist methods to compute confidence intervals and compare estimates of age at the specified length among populations. We provide a parameterization of the von Bertalanffy growth function that has age at a specified length as a parameter. With this parameterization, age at a specified length is directly estimated, and standard methods can be used to construct confidence intervals and make among-group comparisons for this parameter. We demonstrate use of the new parameterization with two data sets.